/**

 * Copyright (c) Meta Platforms, Inc. and affiliates.

 *

 * This source code is licensed under the MIT license found in the

 * LICENSE file in the root directory of this source tree.

 *

 * @flow

 */

import type {Fiber} from './ReactInternalTypes';

import type {StackCursor} from './ReactFiberStack';

import type {Lanes} from './ReactFiberLane';

import {createCursor, push, pop} from './ReactFiberStack';

import {

  getEntangledRenderLanes,

  setEntangledRenderLanes,

} from './ReactFiberWorkLoop';

import {NoLanes, mergeLanes} from './ReactFiberLane';

// TODO: Remove `renderLanes` context in favor of hidden context

type HiddenContext = {

  // Represents the lanes that must be included when processing updates in

  // order to reveal the hidden content.

  // TODO: Remove `subtreeLanes` context from work loop in favor of this one.

  baseLanes: number,

  ...

};

// TODO: This isn't being used yet, but it's intended to replace the

// InvisibleParentContext that is currently managed by SuspenseContext.

export const currentTreeHiddenStackCursor: StackCursor<HiddenContext | null> =

  createCursor(null);

export const prevEntangledRenderLanesCursor: StackCursor<Lanes> =

  createCursor(NoLanes);

export function pushHiddenContext(fiber: Fiber, context: HiddenContext): void {

  const prevEntangledRenderLanes = getEntangledRenderLanes();

  push(prevEntangledRenderLanesCursor, prevEntangledRenderLanes, fiber);

  push(currentTreeHiddenStackCursor, context, fiber);

  // When rendering a subtree that's currently hidden, we must include all

  // lanes that would have rendered if the hidden subtree hadn't been deferred.

  // That is, in order to reveal content from hidden -> visible, we must commit

  // all the updates that we skipped when we originally hid the tree.

  setEntangledRenderLanes(

    mergeLanes(prevEntangledRenderLanes, context.baseLanes),

  );

}

export function reuseHiddenContextOnStack(fiber: Fiber): void {

  // This subtree is not currently hidden, so we don't need to add any lanes

  // to the render lanes. But we still need to push something to avoid a

  // context mismatch. Reuse the existing context on the stack.

  push(prevEntangledRenderLanesCursor, getEntangledRenderLanes(), fiber);

  push(

    currentTreeHiddenStackCursor,

    currentTreeHiddenStackCursor.current,

    fiber,

  );

}

export function popHiddenContext(fiber: Fiber): void {

  // Restore the previous render lanes from the stack

  setEntangledRenderLanes(prevEntangledRenderLanesCursor.current);

  pop(currentTreeHiddenStackCursor, fiber);

  pop(prevEntangledRenderLanesCursor, fiber);

}

export function isCurrentTreeHidden(): boolean {

  return currentTreeHiddenStackCursor.current !== null;

}